Banca de DEFESA: Amanda Santos Vasconcelos

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Amanda Santos Vasconcelos
DATE: 28/06/2024
TIME: 14:00
LOCAL: Auditório 03 / IB
TITLE:

Impacts of small dams on the fish community in the Amazon

KEY WORDS:

culverts; deforestation arc; neotropical fishes, road crossing; small dams

PAGES: 46
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUBÁREA: Ecologia Aplicada
SUMMARY:

Aquatic ecosystem fragmentation by small dams and road crossings poses a significant threat to the biodiversity of lotic environments, such as streams. These structures have an underestimated and understudied impact due to their small size. In Brazil, especially in Mato Grosso, where extensive road networks exacerbate the problem, many unauthorized and undocumented constructions contribute to the fragmentation of water bodies and habitat degradation. Understanding the effects of these barriers on streams and fish biodiversity is crucial, especially in regions like the Amazon, with vast road networks posing significant environmental threats. The present study investigated the effect of these small structures on streams in the Upper Xingu, Brazil, focusing on assessing environmental changes and the impacts of isolation caused by barriers on fish communities. Additionally, we tested the effect of barrier attributes on the environment and fish fauna. Sampling was conducted in pairs, with each stream sampled twice, upstream and downstream, allowing for comparisons. The studied dams were predominantly small, less than 6 meters in height, built between the late 1980s and throughout the 1990s. Environmental differences between treatments were analyzed using Principal Component Analysis (PCA) and Permutational Multivariate Analysis of Variance (perMANOVA). Mixed linear models were used to identify  significant differences in environmental variables between treatments. Total abundance, richness, and
species composition of fish were analyzed using mixed-effects linear models, perMANOVA, and represented by Non-metric Multidimensional Scaling (NMDS). Indicator Species Analysis (ISA) was employed to identify species associated with specific treatments, and the effects of dam characteristics (height and age) on environmental dissimilarity and fish community were tested using simple linear models. Significant differences were observed
between free-flowing (unbarred) streams and disconnected (barred) streams. The analyses showed marked environmental variation in conductivity, dissolved oxygen, and pH parameters among the analyzed stretches. The fish fauna appears not to be significantly affected by the barriers, with total abundance, richness and species composition based on abundance data being similar between analyzed treatments. However, species composition
based on presence/absence data differed significantly, with some species associated with specific locations above or below the barriers. Surprisingly, no effects of barrier characteristics on habitat and fish fauna dissimilarity were found. Our study shows that barriers cause subtle changes in water quality and composition above and below the barriers, but there is no evidence of drastic habitat alterations or local extirpation of species above or below the barriers. Overall, the study provided insights into the impacts of small barriers on stream environments and fish communities, highlighting the importance of considering both environmental and ecological factors in freshwater conservation efforts.

COMMITTEE MEMBERS:
Externa à Instituição - NARAIANA LOUREIRO BENONE - UEMG
Interno - 1210647 - JOSE FRANCISCO GONCALVES JUNIOR
Interno - 1524495 - LUDGERO CARDOSO GALLI VIEIRA